L17 application of inclusive fitness examples Flashcards
What is Hamilton’s rule?
R × b – c > 0, where R = relatedness, b = benefit to recipient’s reproduction, c = cost to actor’s reproduction.
How is Hamilton’s rule expanded for multiple recipients?
Σ(Rᵢ × bᵢ) – C > 0, summing each recipient’s relatedness × benefit minus total cost.
How does Hamilton’s rule handle mixed helping and harming?
Sum of (R × b) terms minus sum of (R × c) terms > 0, or R₁B – r₂C > 0 when comparing helping vs direct reproduction.
According to Hamilton’s rule, toward whom should cooperative behaviours be directed?
Closer relatives (higher R values).
According to Hamilton’s rule, toward whom should harming behaviours be directed?
Away from close kin (lower or negative R impact).
What is kin discrimination?
The ability to direct behaviours based on recognition of relatives versus non-relatives.
What are the two main kin recognition mechanisms?
Genetic cues (e.g., specific alleles or green-beard genes) and environmental cues (e.g., familiarity, shared nest or song dialect).
In long-tailed tits, what choice do helpers make and why?
Failed breeders choose to help nests of kin—identified by song similarity—regardless of distance.
What mechanism underlies kin discrimination in long-tailed tits?
Environmental cue: chicks learn natal song; helpers use song similarity to recognize kin.
Describe the life‐cycle altruism in social amoebae (slime mould).
Under starvation, ~100,000 cells aggregate → migratory slug → fruiting body; ~20% sacrifice to form non-reproductive stalk, elevating kin spores.
Which genes enable kin discrimination in slime mould and how?
tgrB1 and tgrC1 encode matching transmembrane proteins—a green‐beard system ensuring cooperation only with identical alleles.
What did field samples of natural fruiting bodies reveal about slime mould relatedness?
Fruiting bodies are nearly clonal, showing high relatedness among cooperating cells.
What are the two larval morphs of tiger salamanders and their behaviours?
Wild‐type larvae (normal head) and cannibal morph (wide head, sharp teeth) that preys on conspecifics.
How does relatedness influence the emergence of the cannibal morph in tiger salamanders?
Cannibal morphs appear more in low‐related (mixed‐family) groups and preferentially prey on cousins over full siblings.
What key prediction of Hamilton’s rule does the tiger salamander study illustrate?
Harmful behaviour (cannibalism) is directed away from closest kin.
List the four critical empirical examples of kin discrimination covered.
Long-tailed tits (song-based helping), social amoeba (tgr genes in fruiting bodies), tiger salamanders (kin‐dependent cannibalism), plus broad concept of kin discrimination.
What is the empirical goal when testing Hamilton’s rule in nature?
To measure R, b, and c in wild populations and test if R × b – c > 0 predicts cooperation.
In empirical tests of Hamilton’s rule, what two fitness‐maximizing options are compared?
Helping another brood (inclusive fitness = R × b) versus not helping (direct fitness = r₀ × c₀).
In long‐tailed tits, what is the benefit (b) each helper provides to a focal chick?
Each helper increases a chick’s chance of recruiting next year by 0.29.
What is the average relatedness (R) between helpers and breeders in the long‐tailed tit study?
R = 0.16 (slightly closer than cousins).
How is the cost component (c × r₀) quantified in the long‐tailed tit test?
Helping reduces the helper’s own survival, amounting to a 0.48 genetic‐equivalent loss.
What conclusion did the long‐tailed tit study reach regarding Hamilton’s rule?
Despite R × b (0.16×0.29) being less than 0.48, helpers gain net inclusive fitness by assisting, so Hamilton’s rule is satisfied.
Which other taxa have had parameter‐estimation studies confirming R × b exceeds c × r₀?
Bees, wasps, various bugs, turkeys, and tiger salamanders.
What cooperative trait do some mammalian viruses express?
Secretion of interferon‐blocking proteins that protect neighboring virions.
What are the measured cost (c) and benefit (b) for viral interferon‐blockers?
Cost = 0.4 growth reduction for the producer; benefit = 1.6 growth boost for neighbors.
How is the critical relatedness threshold (R*) for viral cooperation calculated?
R* = c / b = 0.4 / 1.6 = 0.25.
Why does interferon‐blocking evolve by kin selection in viruses?
Because viral inocula are largely clonal (R»_space; 0.25), satisfying Hamilton’s rule.
What’s the difference between conditional and fixed cooperation strategies?
Conditional: help chosen case‐by‐case; Fixed: strategy set early and maintained for life.
What does Hamilton’s rule predict about fixed cooperative traits?
They evolve tuned to the average relatedness experienced in the species’ evolutionary history.
How do “staying together” versus “aggregation” group formations differ?
Staying together yields high relatedness (R) and more cooperation; aggregation yields low R and less cooperation.
What did Fisher (2013) find regarding staying‐together vs aggregative microbes?
Clonal (“staying together”) species show more division of labour and sterile cells; aggregative species show less altruistic specialization.
According to Downing (2020), how do family‐based vs aggregative bird cooperators differ in shared paternity?
Family‐based cooperators have lower shared paternity (more helpers per breeder) than aggregative cooperators.
How does a mating system serve as a proxy for relatedness in groups?
Monogamy (single mating) yields high relatedness among nestmates; polyandry (multiple mating) yields lower relatedness (half- or quarter-siblings).
What prediction follows from monogamy versus promiscuity regarding cooperation?
Species with ancestral monogamy should evolve more cooperation than species with promiscuous mating.
In eusocial insects under monogamy, why might a worker help raise siblings instead of reproducing?
Full siblings have r = 0.5, equal to r₀ ≈ 0.5 for own offspring, so helping yields inclusive fitness benefits.
How does multiple mating change siblings’ relatedness and affect worker decisions?
Multiple mating produces half- or step-siblings (r < 0.5), making direct reproduction (r₀ = 0.5) more favorable than helping.
Which avian species illustrate variation in extra-pair paternity and cooperative breeding?
Seychelles warbler (facultative helpers), white-winged choughs (obligate helpers), puffins (low EPP, no helpers), superb fairy wrens (high EPP, but cooperative).
What did the meta-analysis of birds find about promiscuity and cooperative breeding?
Cooperative breeders have significantly lower extra-pair paternity rates than non-cooperative breeders.
Within cooperative bird species, how does extra-pair paternity affect helper occurrence?
The proportion of nests with helpers declines as extra-pair paternity rises.
What does phylogenetic reconstruction reveal about monogamy and cooperative breeding?
Evolutionary transitions to monogamy typically precede the origin of cooperative breeding.
In which lineages is true eusociality found only when ancestry is monogamous?
Eusocial shrimps, bees, and ants all evolved sterile castes in ancestrally monogamous lineages.
What did Griffin (2004) demonstrate about β-lactamase secretion in bacteria?
In high-R populations (single-clone founders), cooperators fix over generations; in low-R (mixed founders), cooperators go extinct.
How do microbial public-goods experiments support Hamilton’s rule?
They show that higher relatedness favors the maintenance of costly cooperative traits, while low relatedness leads to collapse of cooperation.
How can population genetics reveal signatures of cooperation?
By comparing nucleotide diversity: cooperative-gene loci show elevated polymorphism and weaker fixation of beneficial mutations than private-gene loci.
Why are cooperative genes under weaker selection than private genes?
Because benefits accrue to relatives (diluted benefit to the producer), making it harder for cooperative alleles to fix.
How can a high benefit-to-cost (b/c) ratio drive cooperation at low relatedness?
When b/c is large, the net gain (b − c) can favor cooperation even if R is near zero.
Give an example of cooperation evolving at low relatedness due to high b/c.
Algae form non-kin aggregates to avoid predation because the survival benefit outweighs the low relatedness cost.
What types of cooperation can evolve without kinship?
Mutualisms (between species) and low-cost behaviours (e.g., grooming in primates).
Beyond cooperation, what else does inclusive fitness theory predict?
Sex-ratio biases (e.g., fig wasp clutches), worker-policing, and other social traits driven by relatedness.
